In a marine vessel, a propulsion system comprises at least one propeller having a direction of rotation about a drive shaft and a bulbus protrusion extending from the hull associated with each of the at least one propeller, each protrusion extending from the hull of the vessel, each protrusion receiving and rotatably supporting the at least one propeller. Each protrusion extends between leading and trailing ends and has a substantially circular cross section along a length between the leading and trailing ends having and a leading portion extending from the leading end wherein the leading is angled away from the centerline of the hull.

An intentional fluid manipulation apparatus (IFMA) assembly with a first thrust apparatus that imparts a first induced velocity to a local free stream flow during a nominal operation requirement. The first thrust apparatus creates a streamtube. A second thrust apparatus is located in a downstream portion of the streamtube. The second thrust apparatus imparts a second induced velocity to the local free stream flow. The second induced velocity at the location of the second thrust apparatus has a component in a direction opposite to the direction of the first induced velocity at the location of the second thrust apparatus.

A marine propulsion control system for use with a marine vessel, includes a port side engine in electronic communication with a port side engine controller and a starboard side engine in electronic communication with a starboard side engine controller. A control station includes a port lever configured to control a throttle of the port side engine, a starboard lever configured to control a throttle of the starboard side engine, and a user interface. A propulsion control processor is in electronic communication with the port side engine controller, the starboard side engine controller, and control station. In a synchronized operating mode, the propulsion control processor transmits a throttle instruction to the port side engine controller and the starboard side engine controller pursuant to a throttle position of a master lever corresponding to the first of the port lever and starboard lever to be actuated upon activation of the synchronized operating mode.

A marine vessel capable of improving propulsion efficiency for the entire operation of the marine vessel. In the marine vessel, which includes a hull and a propeller provided on a stern side of the hull, n.sup.2D/√(Bd) is 4 or more and 35 or less, in a case where n is the number of the propeller, D is a diameter of the propeller, B is a water line breadth of the hull, and d is a draft of the hull.

A marine vessel capable of improving propulsion efficiency for the entire operation of the marine vessel. In the marine vessel, which includes a hull and a propeller provided on a stern side of the hull, n.sup.2D/√(Bd) is 4 or more and 35 or less, in a case where n is the number of the propeller, D is a diameter of the propeller, B is a water line breadth of the hull, and d is a draft of the hull.

A handheld underwater aircraft includes a battery compartment (12) and propellers. There are at least two propellers, which are symmetrically distributed on both sides of the battery compartment (12), and are connected to the battery compartment (12). A special design with axes of the propellers being unparallel with an axis of the battery compartment (12) is adopted, and unparallel included angles make component forces generated by the various propellers in a direction of motion of a non-underwater aircraft offset each other, and enable the underwater aircraft to maintain balanced and forward-forward motion. The design with the axes of the propellers being unparallel with the axis of the battery compartment (12) leads to a little power loss, but avoids a larger power loss caused by the impact of water on the human body, thereby comprehensively improving the thrust of the underwater aircraft in use.

A handheld underwater aircraft includes a battery compartment (12) and propellers. There are at least two propellers, which are symmetrically distributed on both sides of the battery compartment (12), and are connected to the battery compartment (12). A special design with axes of the propellers being unparallel with an axis of the battery compartment (12) is adopted, and unparallel included angles make component forces generated by the various propellers in a direction of motion of a non-underwater aircraft offset each other, and enable the underwater aircraft to maintain balanced and forward-forward motion. The design with the axes of the propellers being unparallel with the axis of the battery compartment (12) leads to a little power loss, but avoids a larger power loss caused by the impact of water on the human body, thereby comprehensively improving the thrust of the underwater aircraft in use.

A method of de-spinning a rotor of a propulsion system includes providing one or more spinning rotors rotatably mounted on a frame with a bearing having a bearing outer race, bearing balls, and bearing inner race; providing a force mechanism coupled with the one or more spinning rotors for applying a load to the one or more spinning rotors; and loading an outer portion of the outer bearing race, bearing ball, and inner bearing race of the bearing, a load on the outer portion of the bearing race, bearing ball, and inner bearing race of the bearing corresponding to a force applied to the one or more spinning rotors by the drive mechanism. The one or more spinning rotors de-spin at a rate corresponding to the load on the bearing balls.

The invention relates to a drive (10) for a boat as an additional drive or alternative drive to a main drive (20), which is provided with a cavitation plate (24). The drive (10) in this case comprises an electric motor (8) and is designed in such a manner that it can easily be fastened to the main drive. The drive (10) is configured to be fastened to the cavitation plate such that after assembly it does not project rearwards beyond the cavitation plate (24) of the main drive (20).

A vessel (1) comprises a hull (2) including a bow (3) and a stern (4) and has a length-to-beam ratio which is smaller than 10:1, preferably smaller than 5:1. The hull (2) has a vertical centre plane (CP) extending in a direction from the bow (3) to the stern (4). At each side of the centre plane (CP) the vessel (1) has at least two azimuth thrusters (6) including respective propellers (6a), which azimuth thrusters (6) are located next to each other in transverse direction of the centre plane (CP). Each azimuth thruster (6) drivably coupled to its own prime mover (7).